Catalytic conversion of hydrocarbons



- Patented Apr. 7, 1942 UNlTED STATES PATENT OFFICE CATALYTIC commissionor nrnaocsnaoxs Walter F. Hnppke, Lomita, CaliL, assignor to Union OilCompany of Gaiifornia,-Los Angeles, Calif a corporation of California 1"1': Claims. (Cl. 260-683) This invention relates to use of catalystshaving high activity for catalytic dehydrogenation or kindred catalyticprocesses and the like. for example for-the dehydrogenation ofisobutane, n-butane, propane, cyclohexane and similar materials wherebyunsaturates and aromatics and the like may be obtained for the purposes'of production of solvents, motor fuels, and similar sub- -'stances.This application is based upon my co-pending 1 application, Serial No.119,629, filed January 8,

1937, andis a division thereof.

1 have discovered that uranium oxide or vanadium oxide, when used inconjunction with other appropriate materials, is a highly valuabledehydrogenating catalyst for the dehydrogenation of various organicmaterials such as isobutane, nbutane, propane, cyclohexane and similarmaterials obtained from petroleum. I have also discovered, however,that, while uranium oxide or vanadium oxide is a highly active agent forthese purposes, it does not function efliciently if used alone, and itbecomes desirable if not necessary to employ it in conjunction withanother material whichserves to disperse the uranium or vanadium oxideand to impart body and a suitable gel-typestructure of a more or lessvitreous character. For this purpose; aluminum oxide, zirconium oxide orthorium oxide, or mixtures of these, may be employed. Again greaterefliciency may be obtained by employing, in addition to the dispersingor bodying agent, an agent to activate and prolong the life of thecatalyst. For this purpose, zinc oxide is outstanding in that it impartsmuch longer life to these catalysts here described and tends to increasetheir efliciency.

' oxide. Either theoxide for dispersing the catalyst or the activatingand life-prolonging agent maybe omitted or both may be omitted, where itis desired to dispense with either or both of their functions.

- Broadly stated, the invention resides in the dehydrogenation and othertypes of thermal conversion of organic compounds, particularlyhydrocarbons, with a catalyst comprising uranium oxide and a dispersingbodying agent for increasing the gel character of thecatalyst, of

which aluminum, zirconium and thorium oxides life of the catalyst, bothwhere a dispersing and bodying oxide is included and where it is notincluded.

Aside from those aspects of the invention outlined above, I have alsodiscovered that vanadium oxide is ordinarily a good substitute foruranium oxide asthe primary or active agent. Where vanadium oxide isemployed, the other constituents of the catalyst will be employed in thesame respects as above described with respect to uranium oxide, zincoxide being used as the added promoting or activating or life-prolongingagent and aluminum, zirconium and thorium oxides being used as bodyingor distending agents. The invention therefore also resides in theconversion of hydrocarbon and kindred organics with catalysts whereeither of the group consisting of vanadium oxide and uranium oxide isused as the principal catalyst, in conjunction with the dispersing orbodying agent orwith the activating or life-prolonging agent, or withboth types of agents. The invention also extends to such use of a mixturof uranium and vanadium oxides as a catalyst, with or without the othertypes of agents.

In a preferred form of the invention the reduced forms of uranium andvanadium oxides are preferred as being more efficient. The reason forthis preference is that in the presence of hydrocarbon gases to betreated in the presence of the catalyst, for example for dehydrogenationpurposes, when the higher oxide forms are used they are readily reducedand in many instances the oxygen acts upon the hydrocarbons to formobjectionable materials, such as gummy constituents which contaminatethe catalysts and greatly reduce their efiiciency. Of course ininstances where such objectionable materials are not produced or do notaflfect the catalyst, the higher oxide form could be employed.

Considering the practice of this invention, the oxides mentioned maybeproduced in various ways. The preferred procedure residesin-precipitating the hydroxides (or perhaps more properly the hydrousoxides) from solutions of the salts of the metals being employed, thisprecipitation being preferably effected with ammonium hydroxide. Forexample, solutions of mixed nitrates salts of the metals are dissolvedinwater to yield 5 about a 2% solution. This solution usually will beheated to the boiling point and then the dilute aqua ammonia slowlyadded until precipitation is complete. Most of these hydrous oxides areprecipitated in the pH range of 3 to 5. The supernatant l0 liquid isdrawn oi! as the precipitate is settled and the slurry is thentransferred to a Buchner funnel or the like and repeatedly washed ormtered until no more electrolyte can be removed.

At this point the material usually tends to remain in suspension infinely divided form when stirred into water, and when in this fine statemay be termed peptlzed."

These gelatinous precipitates are very adsorptive and by reason of thatcharacteristic may have a small amount of a promoter added thereto insome other .form than the form of these gelatinous precipitatesthemselves, should it be so desired. For example, if a vanadium oruranium salt had not been employed in the precipitation of the hydrousoxides, ammonium metavanadate or uranyl chloride solution maybe stirredinto the gelatinous mass or suspension whereby the salt will be adsorbedor absorbed by the carrier gel. This procedure may be employed so as ameans to add the principal catalyst to the mass, or to add the secondprincipal catalyst thereto if both uranium and vanadium are to beemployed.

After the gelatinous hydrous oxide precipitate has been prepared, thefilter cake is allowed to dry at temperatures around 135' to 150 F.until hard vitreous lumps form. In this drying operation, the gelshrinks to about 5 to 10% of its original wet volume. The lumps soobtained are then broken up and screened, preferably to pass 10 mesh butto stay on a 20 mesh screen. These gel granules are then heated up totemperatures in the order of 650 F. in a large electric tube described.The gel is then dried. The same oxides are obtainable by heating thedried gel when these solutions are adsorbed in the gel as whenoriginally precipitated with the carrier by. droxide's; Other catalyticagents .than uranium and vanadium compounds-may be adsorbed in gels inthe same manner, and a dried gel recovered, which may be used in thatform where appropriate, or heated to convert the salt when required.This procedure is particularly desirable for all those catalytic metalswhich do not easily form insoluble hydrates, which class includesuranium and vanadium. Salts of those metals may be deposited, not onlyin aluminum, zirconium and thorium gels which are precipitated easily byaqua ammonia from solutions of their salts, but also in the gel of anyother metal whose salts readily precipitate gelatinous insolublehydrates with aqua ammonia.

For some uses it is possible to use the catalyst in the form as producedby the stepsabove described, the uranium and vanadium oxides being ofthe higher oxide form. However, for many purposes, ii not for mostpurposes, it is desirable to use catalysts in which such of the uraniumand vanadium oxides as are present are in the reduced form, for thereason that in the presence of hydrocarbon gases the higher oxides passto the reduced form and the oxygen acts to form obiectionable materialssuch as, gummy compounds which damage the catalysts and greatly reducetheir value.

Therefore-in order to obtain the most generally useful form of catalyst,the hard dry gel obtained after drying at 650 F., as above described, isreduced with hydrogen as by placing the gel in a Pyrex or silica tubeand passing dry hydrogen gas therethrough while the temperature is beingraised to about 850 F. The reduced catalyst thus obtained, withouthaving had access to oxygen, may be then employed to perform itscatalytic function. For example, its temperature may be established atany desired operating degree, such as 850 E, and a gas passedthereheater and dry air is slowly passed thereover. through 1 d ation thr of. Bl1 h -8180- With this treatment the gel'will shrink approximatelyone-third more and reach its final volume.

In this form the catalyst constitutes amixture of higher oxides ofuranium and/or vanadium and zinc or such of these as may be employed,such oxides being distributed throughout the aluminum, zirconium orthorium carrier oxide.

The irreducible refractory oxides, that is those of aluminum, thoriumand zirconium, serve to some extent as diluents of the other oxides butare chiefly used because they improve the physical characteristics ofthe catalysts. These oxides all yield gelatinous precipitates whendilute ammonia is added to a dilute solution of their soluble salts.They dry slowly to a hard vitreous gel.

These gels adsorb gases with great avidity, a very excellent property inthe catalyst. When it is desired to incorporate in such a catalystanother ingredient, which of itself does not form gelatinous hydrousoxides, such a gelatinous hydrous oxide washed to remove allelectrolytes are then capable of adsorbing in the cold appreciablequantities of other electrolytes which may be desired in the finishedcatalyst. In addition to those mentioned, vanadyl chloride andnitra'teand uranyl nitrate butane or propane or cyclohexane or other appropriategas. I

In preparing a catalyst, the proportion of the materials used may bevaried very widely. According to a satisfactory procedure, a catalystconsisting of uranium or vanadium oxide, aluminum or zirconium orthorium oxide and zinc oxide may be prepared employing roughly equal molproportions, or in other words portions running about 30 to 40 percenteach of such a three unit mixture.

As an example of the use of a catalyst according to this invention,lsobutane or cyclohexane or other material adapted to dehydrogenationmay be passed in gaseous form through a catalytic body at a temperatureof 850 F. to 950 F. at a rate averaging one second contact time. Therate however, will range from a small fraction of one second to possiblyseveral seconds according to the materials being treated and theconditions.

Working under conditions such as these, cats lysts of the nature abovedescribed have relatively high activity for relatively great lengths oftime at reasonable temperatures. For example, a three-constituentcatalyst as here described, containing uranium oxide or vanadium oxidein a reduced form, when operating at a temperature of about 850 F. willhave a life of and the like may be stirred into the gel above 76 about 8to 10 110111! with m x mum conversion on isobutane of about 18%. Underthese conditions it the promoting catalyst, that is zinc oxide, isomitted, a maximum conversion of about 15% is obtainable or a reductionof 15% to 20% in activity. Again, if the temperature for the threecomponent catalyst is increased to about 950 its life will be decreasedto about 1 to 2 hours, but the conversion ratio will be stepped up toabout 30%; and if the operating temperature is increased to 1050 F. theconversion ratio will be nearly doubled but the life of the catalystwill be still further reduced. In each of these instances the presenceof 30% to-60% of zinc oxide ordinarily increases the life of thecatalyst from 2 to 3 times what it would be in the absence-oi the zincoxide.

I uranium oxides, each of the three oxides being Thus, from the abovestatements, it will be I apparent that while a catalyst containing onlyuranium or vanadium oxide and one of the dispersingoxides such asaluminum or zirconium oxide is good in general as a catalyst, its lifenevertheless is roughly only one-half to one-third that of the catalystcontaining zinc oxide and its activity is around 15% to 20% less thanthat of the catalyst containing zinc oxide. Of course, it is possible touse uranium or vanadium oxide alone, but the importance of itscombination with the various other oxides in the various relationshipsmentioned is apparentwhen it is considered that its conversion capacityat 950 F. is only about 8% or 10% and at 1050 F. is only about 20%. Thusit will be seenrthat the addition of one of the extending or dispersingoxides aluminum, zirconium or thorium oxides, increases the activity asmuch as to 30%, and the presence of zinc oxide prolongs the life perhapstwo to three times as above mentioned.

With respect to the zinc oxide, it is possible that the zinc is presentas a complex oxide with the uranium or vanadium oxide, but I do not wishto be bound by any, theory that the zinc definitely is present in eitherof these forms or in some other form.

The examples and illustrations here given are intended to beillustrative only and it is understood that they are not for the purposeof introducing limitations not required by the restrictions of the priorart.

' I claim: v

1. A method for'the dehydrogenation of hydrocarbons which comprisessubjecting a hydrocarbon to an elevated temperature in the pres ence ofa catalyst comprising an oxide from the class consisting of uranium andvanadium oxides, such oxide being distributed upon an oxide of the classconsisting of aluminum, zirconium and thorium hydrous oxide gels, thecatalyst containing a zinc oxide activator.

2. A dehydrogenation method for hydrocarbons comprising subjecting lighthydrocarbons to elevated temperatures between about 850 F. and 1050 F.in the presence of a catalyst comprising zinc oxide and an oxide fromthe class of uranium and vanadium oxides distributed upon an oxide ofthe class consisting of aluminum, zirconium and thorium oxide gels.

3. A method for the conversion of carbonaceous materials which comprisessubjecting the carbonaceous material in vaporous or gaseous form atelevated temperatures in the order of 850 F. to 1050 F. to the action ofa catalyst comprising zinc oxide, an oxide of the class consisting ofuranium and vanadium oxides and a gel-type oxide of the class consistingof aluminum, zirconium and thorium oxides wherein the w X-i/ I" zincoxide approximates 30% to 60% of the catalyst and the other. oxides arepresent in roughly equal molar proportions.

4. A method for the conversion 01' hydrocarbons comprising subjectinghydrocarbons in gaseous or vaporous form at elevated temperatures to theaction of a catalyst comprising a gel-type oxide from a class ofaluminum, zirconium and thorium oxides and carrying zinc oxide and anoxide of the class consisting of vanadium and present in substantialproportions.

5. A method for the catalytic thermal conversion of petroleumhydrocarbons to change their hydrogen-to-carbon ratio comprisingreacting a hydrocarbon in gaseous or vaporous form at conversiontemperatures in the presence of a catalyst comprising a gel carrier fromthe class consisting of zirconium oxide. aluminum oxide and thoriumhydrous oxide gels, and a catalytic agent carried thereby selected fromthe class consisting of vanadium and uranium oxides, the

catalyst containing zinc oxide in activating proportions.

6. A method'according to claim 5 wherein the three types of constituentsare present in roughly equal molar proportions.

7. A method for the catalytic thermal conversion of hydrocarbons tochange their hydrogento-carbon ratios which comprises subjecting thehydrocarbon in gaseous or vaporous form to conversion temperatures inthe presence of a catalyst comprising a zirconium oxide gel carrier andan active catalytic material carried thereby selected "from the classconsisting of uranium and vanadium catalytic oxides.

8. A methodaccording to claim 7 wherein the catalyst also containscatalytic zinc oxide in activating proportion.

9. A method according to claim 7 wherein the catalyst contains zincoxide as a third constituent, and the three constituents of the catalystare present in roughly equal molar proportions.

10. A method for the conversion of hydrocarbon fractions comprisingsubjecting the hydrocarbon.in the gaseous or vapor form at an elevatedtemperature in the order of 850 F. to 1050 F. to the action of acatalyst comprising a gel-type hydrous oxide carrier containing acatalytic oxide which has been produced by precipitating a hydrous gelwith-an alkaline hydroxide from a solution of a water-soluble salt of ametal from the class consisting of aluminum, zirconium and thorium,filtering and washing the resultant gel-type precipitate until noelectrolyte can be removed, at that point suspending said gelprecipitate in water, stirring into said suspension a solution of awater-soluble salt of a catalytic metal of the class'consisting ofvanadium and uranium whereby the salt is adsorbed by the gelprecipitate, and drying the resultant gel at about 650 F. to 850 F.

1-1. A conversion method according to claim 10 wherein the catalystcontains zinc oxide.

12. A method according to claim 5 wherein the V gel carrier wasprecipitated asa hydrous oxide from solution and a material yielding theoxide of the catalytic metal was deposited upon the precipitated hydrousoxide gel in its original precipitated wet condition before drying.

13. A method according to claim 7 wherein the zirconium oxide gel wasprecipitated from solution as a hydrous oxide and a salt solution of thecatalytic material was deposited upon the 14. A method claim tyzhereincatalyst was produced by precipitating the-ca hvst oxide upon thehydrous .oxide gel whilethe latter was'in an undried state. I v A: 15. Amethod for the dehydrogenation of drocarbons which comprisessubiecting'w'hydro carbon to an elevated temperature in 'the ence of acatalyst comprising an oxide'frozirthe: l0 class'consisting oi uraniumand vanldluni oxidesp. I

such oxide being 'distributedupon an oxide oi. the class consisting oialuminum. mniumg-and thorium hydrous oxide gels, wherein the catalystwas produced by precipitating the cstaiystnxide.

upon the hydrous oxide gel while theiiatte'rjnag in an undried state.

'18; A method for the catalyticthermal version? of petroleumhydrocarbons 1 to change their hydrogen-'to-carbon ratio communeacting5a hydrocarbon in gaseous orwaporous iornr atconversion temperaturesin-thepresfence o 'iiiv aii the class" consisting of zirconium, aluminumand hydrous oxide gels, and a catalytic vagentcarried therebyselectedfrom the. class consisting of vanadium uranium oxides,

whereinthe gel carrier was precipitated from Gj'olution as ahydrousoxide. and wherein the catalytic metal was deposited upon theprecipitated hydrous oxide gelinits original precipitated wet conditionbefore drying.

-- 17. A method according to claim 1 wherein the gel carrier wasprecipitated from solution and the catalytic metakoi'said classconsisting of uranium and vanadium was deposited upon the gel carrier ina form to yield'said catalytic oxides or said class consisting oiuranium and vanadium oxides, said form of the'catalytic metal beingdeposited"upon' the gel carrier while the precipita'ted gel was still inits original wet and'un-- dried-state. r i trauma runopm.

